Sutchin R. Patel

Automated renal stone volume measurement by noncontrast computerized tomography is more reproducible than manual linear size measurement.

PURPOSE We compared the reproducibility of automated volume and manual linear measurements using same study supine and prone, low dose, noncontrast computerized tomography series. MATERIALS AND METHODS The patient cohort comprised 50 consecutive adults with a mean age of 56.4 years in whom renal calculi were identified during computerized tomography colonography screening. The largest stone per patient was assessed with the supine and prone computerized tomography series serving as mutual controls. Automated stone volume was derived using a commercially available coronary artery calcium scoring tool. Supine-prone reproducibility for automated volume was compared with intra-observer supine-prone manual linear measurement. Interobserver variability was also assessed for manual linear measurements of the same supine or prone series. RESULTS Mean ± SD linear size and volume of the 50 index calculi was 4.5 ± 2.7 mm (range 1.8 to 16) and 141.7 ± 456.1 mm(3), respectively. The mean supine-prone error for automated stone volume was 16.3% compared with an average 11.7% 1-dimensional intra-observer error for manual axial measurement. Only 2 of 15 cases with a volume error of greater than 20% were 5 mm or greater in linear size. The average interobserver linear error for the same computerized tomography series was 26.3% but automated volume measurement of the same series did not vary. CONCLUSIONS Automated noncontrast computerized tomography renal stone volume is more reproducible than manual linear size measurement and it avoids the often large interobserver variability seen with manual assessment. Since small linear differences correspond to much larger volume changes, greater absolute volume errors are acceptable. Automated volume measurement may be an improved clinical parameter to use for following the renal stone burden.

Clinical, Pathologic, and Functional Outcomes After Nephron-Sparing Surgery in Patients with a Solitary Kidney: A Multicenter Experience

BACKGROUND AND PURPOSE Surgical management of a renal neoplasm in a solitary kidney is a balance between oncologic control and preservation of renal function. We analyzed patients with a renal mass in a solitary kidney undergoing nephron-sparing procedures to determine perioperative, oncologic, and renal functional outcomes. PATIENTS AND METHODS A multicenter study was performed from 12 institutions. All patients with a functional or anatomic solitary kidney who underwent nephron-sparing surgery for one or more renal masses were included. Tumor size, complications, and recurrence rates were recorded. Renal function was assessed with serum creatinine level and estimated glomerular filtration rate. RESULTS Ninety-eight patients underwent 105 ablations, and 100 patients underwent partial nephrectomy (PN). Preoperative estimated glomerular filtration rate (eGFR) was similar between the groups. Tumors managed with PN were significantly larger than those managed with ablation (P<0.001). Ablations were associated with a lower overall complication rate (9.5% vs 24%, P=0.01) and higher local recurrence rate (6.7% vs 3%, P=0.04). Eighty-four patients had a preoperative eGFR ≥60 mL/min/1.73 m(2). Among these patients, 19 (23%) fell below this threshold after 3 months and 15 (18%) at 12 months. Postoperatively, there was no significant difference in eGFR between the groups. CONCLUSIONS Extirpation and ablation are both reasonable options for treatment. Ablation is more minimally invasive, albeit with higher recurrence rates compared with PN. Postoperative renal function is similar in both groups and is not affected by surgical approach.

Hydrodissection Using an Iodinated Contrast Medium During Percutaneous Renal Cryoablation

We describe our experience using an iodinated contrast solution to hydrodissect adjacent structures before percutaneous renal cryoablation. Hydrodissection was performed before cryoablation with placement of a 20-gauge, 15-cm introducer needle into the retroperitoneum under CT or ultrasonographic guidance followed by infusion of 5% dextrose in water and 2% iodinated contrast between the kidney and the adjacent organ. Ten patients underwent hydrodissection with an iodinated contrast solution at our institution. The mean tumor size was 3.1 ± 1.2 cm. The organs displaced included colon (n=7), small bowel (n=1), pancreas (n=1), and in one case, both the colon and ureter were displaced. The average displacement of all organs from the kidney was 2.8 cm (range 2.2-3.5 cm). There were no complications and no injuries to any adjacent structures. The injection of iodinated contrast allows for safe mobilization and differentiation of adjacent structures from the renal tumor and parenchyma leading to potentially safer cryoablation.

Dietary induction of long-term hyperoxaluria in the porcine model.

PURPOSE The purpose of our study was to determine if a hydroxyproline (HP) or gelatin diet could induce long-term hyperoxaluria in the porcine model. MATERIALS AND METHODS A total of 18 gravid crossbred sows (Large White × Landrace) were randomly allotted into three treatment groups: 5% HP, 10% HP, and gelatin diet. All sows were catheterized 1 day before starting treatment diet. Catheters were left in place for 5 days before being removed. Sows were recatheterized for urine collections on days 11 to 12 and days 21 to 22. Urine was collected for each entire 24-hour period, and urinary oxalate was determined by ion chromatography. RESULTS Urinary oxalate concentrations for all three diets peaked within the first 5 days of the diet. The sows fed the 5% HP, 10% HP, and gelatin diets had an early peak in urinary oxalate concentration (mg/L) at day 2 (158% increase), day 5 (316% increase), and day 5 (830% increase), respectively. The day 21 to 22 time points in all three diets demonstrated markedly increased urinary oxalate concentrations in comparison with baseline, with some concentrations higher than the early time point peaks (day 22: 5% HP=1906% increase, P=0.12; 10% HP=640% increase, P=0.02; gelatin=501% increase, P=0.01). CONCLUSION Although both the 10% HP and gelatin diets induce significant short- and long-term hyperoxaluria in the porcine model, the gelatin diet is more cost-effective. The ability to induce long-term hyperoxaluria has important implications in establishing a porcine model for oxalate urolithiasis.

Automated Volumetric Assessment by Noncontrast Computed Tomography in the Surveillance of Nephrolithiasis

OBJECTIVE To evaluate the use of automated volumetric assessment for stone surveillance and compare the results with manual linear measurement. METHODS We retrospectively reviewed patients seen in our stone clinic who had undergone 2 noncontrast computed tomography (NCCT) scans without stone intervention during the interval between scans. Thirty patients met our inclusion criteria and underwent longitudinal assessment for urolithiasis via NCCT (mean interval 583.2 days, range 122-2030). Fifty-two discrete calculi were analyzed. Three board certified radiologists measured maximal linear stone size in the axial plane using electronic calipers on soft tissue (ST) and bone windows (BWs). Automated stone volume was also obtained by each reader using a dedicated prototype software tool for stone evaluation. RESULTS Mean stone linear size and volume was 4.9 ± 2.8 mm (ST), 4.5 ± 2.6 mm (BW), and 116.2 ± 194.6 mm(3) (window independent), respectively. Mean interobserver variability for linear size measurement was 16.4 ± 10.5% (ST) and 20.3 ± 13.8% (BW). Interobserver variability for volumetric measurement was 0%. Of the 52 persistent stones, the mean percent change in linear stone size between CT studies was 39.3 ± 46.7% (ST) and 42.9 ± 53.1% (BW) growth, compared with 171.4 ± 320.1% (window independent) growth for automated volume measurement over a mean of 583.2 days. However, discordant results for increased vs decreased interval size was seen between linear and volumetric assessment in 19/52 stones (36.5%). CONCLUSION Automated volumetric measurement of renal calculi via NCCT is independent of specific reader and window settings. Volumetric assessment amplifies smaller linear changes over time, whereas as much as one third of cases show linear-volume measurement discordance. Volumetric assessment is therefore preferable, particularly for longitudinal surveillance of renal calculi.

Skill Based Mentored Laparoscopy Course Participation Leads to Laparoscopic Practice Expansion and Assists in Transition to Robotic Surgery

PURPOSE Prior studies suggest poor long-term incorporation of laparoscopy into urology practice after a postgraduate course. We evaluated the influence of the American Urological Association Mentored Laparoscopy Course on urologist clinical practice. MATERIALS AND METHODS The 2-day Mentored Laparoscopy Course includes lectures, standardized dry laboratory training with videotape analysis and a porcine laboratory with consistent mentors. Surveys to assess the impact of the course were sent in April 2010 to the 153 urologists who had taken the course from 2004 through 2009. RESULTS Of the 153 surveys 91 (60%) were returned a mean of 34.5 months after completing the course. Of the respondents 82% were in a group private practice, followed by solo private practice (15%) and full-time academic practice (3%). Of the respondents 92% reported that they had sutured laparoscopically, 52% had sutured a bleeding vessel and 51% had performed reconstructive laparoscopy since taking the course. Of the respondents 77% reported that their laparoscopic practice had expanded since taking the course (mean 2.9 cases monthly). Of the 41 respondents (45%) who now performed robotic surgery (mean 3.8 cases monthly) 39 (95%) thought that the course experience had helped with the transition into robotic surgery. Overall survey respondents were pleased with the experience during the course with 89 of 91 (98%) stating that they would recommend the course to a colleague. CONCLUSIONS Long-term results reveal that the American Urological Association Mentored Laparoscopy Course attendees reported expansion in their laparoscopic practice since taking the course. They described the course as benefiting the transition to robotic surgery.

Trends in the medical management of urolithiasis: a comparison of general urologists and endourology specialists.

OBJECTIVES To determine whether there are differences in the medical and dietary recommendations given to stone formers between urologists that subspecialize in endourology and general urologists. METHODS A 10 question on-line survey was sent via e-mail to members of the North Central Section (NCS) of the American Urological Association and the Endourological Society (ES). RESULTS A total of 206 surveys were completed by members of the NCS and 122 surveys were completed by members of the ES. Of the ES members, 75% were in academic practice versus 21% of NCS members (P < .01). Urologists in both groups performed their own medical management (88% ES, 83% NCS) and believed that they were able to provide effective dietary recommendations (73% ES, 72% NCS). Most urologists in both groups performed 24-hour urine and serum studies in recurrent stone formers (68% ES, 73% NCS) as opposed to all stone formers (17% ES, 18% NCS). Members of both groups recommended low salt intake to all stone formers (68% ES, 61% NCS) or only calcium stone formers (18% ES, 29% NCS; P = .03). A higher percentage of urologists from the ES recommended low animal protein intake to all stone formers than urologists from the NCS (69% ES, 47% NCS; P < .05). CONCLUSIONS Urologists from both the NCS and the ES, despite differences in the type of practice, subspecialty interest in endourology and geographic location of practice, have similar medical and nutritional practices when counseling patients in the prevention of stone disease.

The History and Development of Percutaneous Nephrolithotomy

The standard treatment for patients with renal calculi prior to the mid 1950s was open stone surgery. The existence of a relatively avascular plane 5 mm posterior to the midline of the kidney was establish through the work of Joseph Hyrtl in 1882 and Max Brodel in 1902. It was not until 1941, that Rupel and Brown would perform the first nephroscopy by placing a rigid cystoscope through a nephrostomy tract so that stones could be removed during open surgery. Willard Goodwin , in 1955, is credited with performing the first nephrostomy tube placement. By 1976 Fernstrom and Johansson were the first to describe a technique for extracting renal calculi through a percutaneous nephrostomy under radiologic control. In 1978, Arthur Smith would describe the first antegrade stent placement and would coin the term “endourology” to describe closed, controlled manipulation of the genitourinary tract. His collaboratoin with Kurt Amplatz, an interventional radiologist and medical inventor, would lead to numerous innovations which would further advance percutaneous nephrolithotmy (PCNL). Advances in radiology, from improvements in fluoroscopy to the use of pre-operative computed tomography would further aid in renal access. The development of various lithotripsy devices and the introduction of the holmium laser improved the efficacy of stone fragmentation and clearance. Numerous factors contributed to development of the modern day PCNL and this technique will continue to evolve in the future.

The History of Percutaneous Renal Cryoablation

The increased use of cross-sectional imaging has led to an increase in the detection of suspected renal cell carcinoma at an early stage. The development of ablative techniques has led to an increase in treatment options for patients with small renal masses (≤4 cm). Percutaneous renal cryoablation has evolved into a minimally invasive treatment option for select lesions and for the high risk surgical patient. In this chapter we chronicle the early development of cryoablation and its application for the treatment of renal masses.

Strategies for Providing Nutritional Therapy and Education to Stone-Forming Patients

The AUA guidelines on the medical management of kidney stones specify that when obtaining a dietary history from a patient, one should elicit “their daily intake of fluids (amount and specific beverages), protein (types and amounts), calcium, sodium, high oxalate-containing foods, fruits and vegetables and over-the-counter supplements” [1]. Approximately three-quarters of urologists (72%) believe that they are able to provide effective dietary recommendations [2]. At the same time, urologists and other providers have identified lack of time, nutrition knowledge and dietary assessment, and interviewing skills as barriers to providing tailored nutritional counseling [3]. Patients’ understanding of dietary recommendations may improve when they are given personalized or tailored recommendations [4]. Registered dietician nutritionists (RDNs) are trained to take detailed dietary histories utilizing food intake questionnaires and generally have more time to obtain this information from patients than a practicing urologist or nephrologist as well as provide a more customized nutritional counseling plan [5]. Thus having an RDN can further augment one’s ability to identify dietary factors implicated in stone recurrence and provide customized nutritional counseling [5]. A multidisciplinary approach to nutritional counseling may also be more effective due to an observed phenomenon called the stone clinic effect [6]. Jhagroo et al. developed a shared medical appointment model to improve access as well as patient education and exposure to multidisciplinary care [7]. By incorporating presentations and multidisciplinary rounding in a group setting, patients’ post-tests revealed that the patients in shared medical appointments had superior knowledge (p < 0.02) as well as higher patient satisfaction than the control patients. Another effect of the shared medical appointment was a decrease in appointment wait time and an increase in the number of patients seen per month (43% increase) [7].